Lee Merideth at Leethal Knits has designed wonderful patterns. Her patterns can often be made in many different weights of yarn, for very different effects. I've made her Wild Is The Wind, Barry, and Misanga hats recently, and would recommend each one.
Sashka Macievich of Sashka Knits designed the Syxx hat, which I made and enjoyed as well
Certainly Elizabeth Zimmermann and Meg Swansen are both amazing inspirations, from my own home state of Wisconsin. I also have loved designing patterns from Barbara Walker's stitch dictionaries, which are very comprehensive and encourage the reader to use her own head to come up with even more. Alice Starmore has amazing colorwork designs that one can use to create lovely patterns